Silk treatment



Patented Apr. 6, 1948 SILK TREATMENT Ben W.'Row1and and ton, Wis., assignors Chemistry, Appleton, Wis,

Wisconsin Douglas Fronmuller, Appleto The-Institute of Bayer a o oration 1 No Drawing. Application June 14, 1940,

"Serial No. 340,573

The present invention relates generally to the treatment of silk and more specifically to the step in the processing of silk known inthe art asthe throwing operation.

The principal object of the present invention isto provide silk processing treatments which serve as practical means for obtaining improved silk.

Other objects will be apparent as the description hereinafter proceeds.

Heretofore, in processing silk for use in the art as, for example, in the manufacture of silk hosiery, it has been customary practive to carry out all chemical processing treatments in alkaline baths. Anillustrativeexample is the throwing bath used in the throwing operation, i. e., a processing step employed to loosen up and soften the individual strands of raw silk to the extent that the skein of silk can be reeled off onto a reel prior to twisting and coning. The silk obtained after treatment in such baths (particularly the throwing bath where the silk remains in contact with the alkali for some time) has long been recognized by the art as relatively unsatisfactory. We discovered after an extended investigation that acid throwing baths having pH values between .3 to 5.8 andpreierablyaround 3.45 provide practicalmeans for obtaining improved silk.

.For example, hosiery made from the silk processedin theacidbaths of the present invention,

has improved stretch and tensile strength characteristics, improved form-fitting, e. g. less slackening at the knees aiteraperiod of wear, and exhibits a definitelycleaner knitting stitch.

The throwing baths'are aqueous baths con:

taining small amounts of (l) a softening oil such as mineral oil, cocoanut oil, etc., in emulsified form, and (2) an acidic material such as glyceryl lauryl sulphate, acetic acid, etc. The preferred baths also contain a penetrating agent such as a surface-active alkali metal sulphate or sulphonate or a phospholipoid such as lecithin. Materials of this type in addition to penetrating action may aid in the emulsification of the oil as well as serve as acidic buffers. The following representative baths or throwing emulsions will serve for illustrative purposes.

Emulsion 1 A bath composed of about 100 parts of water, about 0.5 part of the sodium salt of monoglyceryllauryl sulphate, about 2.5 parts of mineral oil and sufficient monoglyceryl-lauryl sulphate to adjust the pH of the mixture to about 3.45. In this emulsion the ingredients are added in the usual man- 2 nor andafter mixing the bath is stirred .vigorously, or passed through ,a colloid mill in order to emulsify the oil.

a I I .Em s Qn 2 A b athljcomposed of about 200 parts of water,

about 10 parts oilecithin oiland sufficient acetic acid buffered by sodiumacetate ,to adjust the pH of the mixture to a range of about 3.0 to 5.5

In this emulsion the acidic-material is preferably added after the water and lecithin oil'have been heated, e. g. to 50-60 C; and stirred vigorously in order to emulsify the oil. The lecithin oil referred to herein isacrude lecithin composition containing about .40 to per cent cocoanut oil.

Emulsion 3 A bath composed of about 200 parts water, aboutj5 parts lecithin, about 5 parts mineral oil and sufiicient acidic material such ,as acetic acid containinga buffer. suchas sodium acetate toadjust the pHof the mixture toarange of about 3.0 to 5.5. Inthis emulsion the in ledientsmay be added in :the usual manner and the bath stirred vigorously in order toemulsifytheoil in accordance with the above examples.

E uls A bath composed of about parts water, 0.5

part of :thesodium salt of monoglyceryl-lauryl sulphate, 1.25parts mineral oil, 1".25 parts of 50 per cent sulphonated castor oil, and sufficient acetic acid to adiust the pH of the mixture to 3.45. This mixture is agitated sufliciently in the usual manner to form a stable emulsion consisting of small (1 1 sizes.

It will be understood that the present invention is not limited to the above illustrative examples. For example, in place of the oils listed above other softening oils may be employed, although the use of a relatively inert aliphatic oil is generally preferred. In place of glyceryl lauryl sulphate, other materials such as sulphated cottonseed oil, sulphonated castor oil (Turkey red oil), oleyl sulphate and an alkyl aryl sulphate sold in the trade as Nacconal may be used if desired. In place of acetic acid, other acidic materials such as citric acid may be employed. The acidic material in any event should be present in suflicient amount to adjust and maintain the pH value to approximately 3.0-3.3 to 5.5-5.8. v

The following comparative tests results obtained with silk processed in (1) the standard alkaline throwing bath and (2) the new acid throwing bath will serve to illustrate the improveinents obtainable by processing silk in accordance with the present invention.

The above tests were carried out after coning on at Scott inclined plane tester. The test'siree been made on the oil pickup in throwing baths containing the same amount of available oil and it was found that 94 per cent of the available oil was taken up in an acid bath in a given period while only 31 per cent of the available oil was taken up in the same period in an alkaline bath.

'The throwing operation of the present inven tion may be carried out on raw silk, although it sults which are representativeshowa 'IO O -per cent increase in stretch and about a 20" percent improvement in tensile strength.

Table II Alkaline 'Acid j Thrown Thrown Silk Silk Variation on a 30 inch length .l.0 in-. :25 in.

The above tests were carried out after knitting on commercial equipment, the alkaline and acid thrown silks being run side-by side in the same room (under the, same conditions, e. g.-humidity, etc.) on the same machine bank. The measurements were madeon the length of the legs of the knitted hosiery.

' Table III Alkaline Acid Thrown l'lhrown Silk Silk Average Wearing Life Ratio-- 200 hours 600 hours.

The above tests were carried out on Tsilk stockings after-the usual alkaline-soap boilofij i. e. removal of silk waxes, and dyeing operation. The stockings made from acid thrown silk in addition to the remarkable increase in wearing life also exhibited improved washability.

Our investigations indicate that the throwing operation i. e.treatment of the silk, should be carried out in the acidbaths of the present invention at about 70-100 F. for about to 30 minutes. Ordinarily a temperature of about 80 F. is preferred and a treatment or soaking period of about minutes adequate, as pur investigation shows that thesilk takes up the available oil much more readily in the acid baths of the present invention than in the'standard alkaline throwing baths employed heretofore. Comparative measurements, for example, have .is preferred to practice the process of the present'inventlon in combination with the preliminary acid rinse process described and claimed in our copending application Serial No. 340,572,

now abandoned. Such a combined process in- 'cludes (1), an initial treatment of raw silk with a bath having a pH value of 3.5 to 5.5 and consisting of water, acidic material and a buffer, i. e.

flingthe absence of oil, and (2) followed by an acidic throwing treatment in the presence of oil as herein described.

It will be understood that the present invention is not limited to the above illustrative examples. All modifications coming within the scope of the present invention are intended to be covered by the following claim.

We claim:

In the art of processing silk, the improvement which comprises subjectingsilk to a treatment in an aqueous bath consisting of a mineral oil emulsion, a small amount of the sodium salt of monoglyceryl-lauryl sulphate, a small amount of sulphonated castor oil and suificient acetic acid to adjust the pH value of said bath toabout 3.45. a BEN W. ROWLAND.

DOUGLAS FRONMULLER;

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Date OTHER REFERENCES TextileResearch, Cambridge, 1932, U. S. Institute for Textile Research, pages 157, 167. La Motte: The ABC of Hydrogen Ion Control, 5th 'ed., Baltimore, 1929, pages 45 and 46. 

